Integrate with ElementInternals

Closes [basecamp#1023][]

Replace the requirement for an `<input type="hidden">` element with
direct `<form>` integration through built-in support for
[ElementInternals][].

According to the [Form-associated custom elements][] section of [More
capable form controls][], various behaviors that the `<trix-editor>`
element was recreating are provided out of the box.

For example, the `<input type="hidden">`-`[input]` attribute pairing can
be achieved through [ElementInternals.setFormValue][]. Similarly, the
`<label>` element support can be achieved through
[ElementInternals.labels][].

[basecamp#1023]: basecamp#1023
[ElementInternals]: https://developer.mozilla.org/en-US/docs/Web/API/ElementInternals
[Form-associated custom elements]: https://web.dev/articles/more-capable-form-controls#form-associated_custom_elements
[More capable form controls]: https://web.dev/articles/more-capable-form-controls
[ElementInternals.setFormValue]: https://developer.mozilla.org/en-US/docs/Web/API/ElementInternals/setFormValue
[ElementInternals.labels]: https://developer.mozilla.org/en-US/docs/Web/API/ElementInternals/labels

.github/workflows/ci.yml

@@ -8,8 +8,13 @@ on:
 
 jobs:
   build:
-    name: Browser tests
+    name: "Browser tests (formAssociated: ${{ matrix.formAssociated }})"
     runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        elementInternals: [false, true]
+    env:
+      EDITOR_FORM_ASSOCIATED: "${{ matrix.formAssociated }}"
     steps:
       - uses: actions/checkout@v3
       - uses: actions/setup-node@v3

README.md

@@ -19,7 +19,7 @@ This is the approach that all modern, production ready, WYSIWYG editors now take
 
 <details><summary>Trix supports all evergreen, self-updating desktop and mobile browsers.</summary><img src="https://app.saucelabs.com/browser-matrix/basecamp_trix.svg"></details>
 
-Trix is built with established web standards, notably [Custom Elements](https://developer.mozilla.org/en-US/docs/Web/Web_Components/Using_custom_elements), [Mutation Observer](https://dom.spec.whatwg.org/#mutation-observers), and [Promises](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise).
+Trix is built with established web standards, notably [Custom Elements](https://developer.mozilla.org/en-US/docs/Web/Web_Components/Using_custom_elements), [Element Internals](https://developer.mozilla.org/en-US/docs/Web/API/ElementInternals), [Mutation Observer](https://dom.spec.whatwg.org/#mutation-observers), and [Promises](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise).
 
 # Getting Started
 
@@ -49,12 +49,26 @@ document.addEventListener("trix-before-initialize", () => {
 
 ## Creating an Editor
 
-Place an empty `<trix-editor></trix-editor>` tag on the page. Trix will automatically insert a separate `<trix-toolbar>` before the editor.
+Place an empty `<trix-editor></trix-editor>` tag on the page. If the `<trix-editor>` element is rendered with a `[toolbar]` attribute that references the element by its `[id]`, it will treat that element as its toolbar:
+
+```html
+<trix-toolbar id="editor_toolbar"></trix-toolbar>
+
+<trix-editor toolbar="editor_toolbar"></trix-editor>
+```
+
+Otherwise, Trix will automatically insert a separate `<trix-toolbar>` before the editor.
 
 Like an HTML `<textarea>`, `<trix-editor>` accepts `autofocus` and `placeholder` attributes. Unlike a `<textarea>`, `<trix-editor>` automatically expands vertically to fit its contents.
 
 ## Integrating With Forms
 
+There are two styles of integrating with `<form>` element submissions.
+
+### Legacy integration with `<input type="hidden">`
+
+Legacy support is provided through an `<input type="hidden">` element paired with an `[input]` attribute on the `<trix-editor>` element.
+
 To submit the contents of a `<trix-editor>` with a form, first define a hidden input field in the form and assign it an `id`. Then reference that `id` in the editor’s `input` attribute.
 
 ```html
@@ -66,7 +80,7 @@ To submit the contents of a `<trix-editor>` with a form, first define a hidden i
 
 Trix will automatically update the value of the hidden input field with each change to the editor.
 
-## Populating With Stored Content
+#### Populating With Stored Content
 
 To populate a `<trix-editor>` with stored content, include that content in the associated input element’s `value` attribute.
 
@@ -79,6 +93,44 @@ To populate a `<trix-editor>` with stored content, include that content in the a
 
 Always use an associated input element to safely populate an editor. Trix won’t load any HTML content inside a `<trix-editor>…</trix-editor>` tag.
 
+### Integration with Element Internals
+
+Trix can also be configured to integrate with forms through the `<trix-editor>` element's `ElementInternals` instance.
+
+First, configure Trix to opt-into its Element Internals support by rendering a `<meta>` element into the document's `<head>`:
+
+```html
+<head>
+  <!-- … -->
+  <meta name="trix-editor-formAssociated" content="true">
+</head>
+```
+
+Then, to submit the contents of a `<trix-editor>` with a `<form>`, render the element with a `[name]` attribute and its initial value as its inner HTML.
+
+```html
+<form …>
+  <trix-editor name="content"></trix-editor>
+</form>
+```
+
+To associate the element with a `<form>` that isn't an ancestor, render the element with a `[form]` attribute that references the `<form>` element by its `[id]`:
+
+```html
+<form id="a-form-element" …></form>
+<trix-editor name="content" form="a-form-element"></trix-editor>
+```
+
+#### Populating With Stored Content
+
+To populate a `<trix-editor>` with stored content, include that content as HTML inside the element’s inner HTML.
+
+```html
+<form …>
+  <trix-editor>Editor content goes here</trix-editor>
+</form>
+```
+
 ## Providing an Accessible Name
 
 Like other form controls, `<trix-editor>` elements should have an accessible name. The `<trix-editor>` element integrates with `<label>` elements and The `<trix-editor>` supports two styles of integrating with `<label>` elements:

assets/index.html

@@ -12,7 +12,7 @@
         box-sizing: border-box;
       }
 
-      main {
+      main, nav {
         margin: 20px auto;
         max-width: 700px;
       }
@@ -69,8 +69,27 @@
         }
       });
     </script>
+    <script>
+      const searchParams = new URLSearchParams(location.search)
+
+      if (searchParams.get("editor") === "formAssociated") {
+        document.head.insertAdjacentHTML(
+          "beforeend",
+          `<meta name="trix-editor-formAssociated" content="true">`
+        )
+
+        document.addEventListener("trix-change", function(event) {
+          var input = document.getElementById("input")
+          input.value = event.target.value
+        })
+      }
+    </script>
   </head>
   <body>
+    <nav>
+      <a href="/">Legacy support</a>
+      <a href="/?editor=formAssociated">ElementInternals support</a>
+    </nav>
     <main>
       <label for="editor">Input</label>
       <trix-editor autofocus class="trix-content" input="input" id="editor"></trix-editor>

karma.conf.js

@@ -101,6 +101,10 @@ if (process.env.SAUCE_ACCESS_KEY) {
   }
 }
 
+if (process.env.EDITOR_FORM_ASSOCIATED === "true") {
+  config.files.unshift({ pattern: "src/test/test_helpers/fixtures/form_associated.js", watched: false, included: true })
+}
+
 function buildId() {
   const { GITHUB_WORKFLOW, GITHUB_RUN_NUMBER, GITHUB_RUN_ID } = process.env
   return GITHUB_WORKFLOW && GITHUB_RUN_NUMBER && GITHUB_RUN_ID

src/test/system/accessibility_test.js

@@ -1,4 +1,5 @@
-import { assert, test, testGroup, triggerEvent } from "test/test_helper"
+import * as config from "trix/config"
+import { assert, test, testGroup, testIf, testUnless, triggerEvent } from "test/test_helper"
 
 testGroup("Accessibility attributes", { template: "editor_default_aria_label" }, () => {
   test("sets the role to textbox", () => {
@@ -22,17 +23,26 @@ testGroup("Accessibility attributes", { template: "editor_default_aria_label" },
     assert.equal(editor.getAttribute("aria-labelledby"), "aria-labelledby-id")
   })
 
-  test("assigns aria-label to the text of the element's <label> elements", () => {
+  testUnless(config.editor.formAssociated, "assigns aria-label to the text of the element's <label> elements", () => {
     const editor = document.getElementById("editor-with-labels")
     assert.equal(editor.getAttribute("aria-label"), "Label 1 Label 2 Label 3")
   })
 
-  test("updates the aria-label on focus", () => {
+  testUnless(config.editor.formAssociated, "updates the aria-label on focus", () => {
     const editor = document.getElementById("editor-with-modified-label")
     const label = document.getElementById("modified-label")
 
     label.innerHTML = "<span>New Value</span>"
     triggerEvent(editor, "focus")
     assert.equal(editor.getAttribute("aria-label"), "New Value")
   })
+
+  testIf(config.editor.formAssociated, "does not set [aria-label] for a <label> element", () => {
+    const editor = document.getElementById("editor-with-labels")
+    const labels = Array.from(editor.labels)
+    const text = labels.map((label) => label.textContent.trim())
+
+    assert.deepEqual(text, [ "Label 1", "Label 2", "Label 3" ])
+    assert.equal(editor.getAttribute("aria-label"), null)
+  })
 })

src/test/system/custom_element_test.js

@@ -1,3 +1,4 @@
+import * as config from "trix/config"
 import { rangesAreEqual } from "trix/core/helpers"
 
 import {
@@ -13,6 +14,7 @@ import {
   test,
   testGroup,
   testIf,
+  testUnless,
   triggerEvent,
   typeCharacters,
   typeInToolbarDialog,
@@ -510,12 +512,12 @@ testGroup("<label> support", { template: "editor_with_labels" }, () => {
     assert.deepEqual(Array.from(getEditorElement().labels), labels)
   })
 
-  test("focuses when <label> clicked", () => {
+  testUnless(config.editor.formAssociated, "focuses when <label> clicked", () => {
     document.getElementById("label-1").click()
     assert.equal(getEditorElement(), document.activeElement)
   })
 
-  test("focuses when <label> descendant clicked", () => {
+  testUnless(config.editor.formAssociated, "focuses when <label> descendant clicked", () => {
     document.getElementById("label-1").querySelector("span").click()
     assert.equal(getEditorElement(), document.activeElement)
   })

src/test/system/installation_process_test.js

@@ -1,6 +1,7 @@
+import * as config from "trix/config"
 import EditorController from "trix/controllers/editor_controller"
 
-import { assert, test, testGroup } from "test/test_helper"
+import { assert, test, testGroup, testUnless } from "test/test_helper"
 import { nextFrame } from "../test_helpers/timing_helpers"
 
 testGroup("Installation process", { template: "editor_html" }, () => {
@@ -31,7 +32,7 @@ testGroup("Installation process without specified elements", { template: "editor
     assert.equal(editorElement.toolbarElement, toolbarElement)
   })
 
-  test("creates identified input elements", () => {
+  testUnless(config.editor.formAssociated, "creates identified input elements", () => {
     const editorElement = getEditorElement()
 
     const inputId = editorElement.getAttribute("input")

src/test/test_helpers/fixtures/editor_html.js

@@ -1,3 +1,8 @@
+import * as config from "trix/config"
+
 export default () =>
-  `<input id="my_input" type="hidden" value="&lt;div&gt;Hello world&lt;/div&gt;">
-  <trix-editor input="my_input" autofocus placeholder="Say hello..."></trix-editor>`
+  config.editor.formAssociated ?
+    `<trix-editor autofocus placeholder="Say hello..."><div>Hello world</div></trix-editor>
+    ` :
+    `<input id="my_input" type="hidden" value="&lt;div&gt;Hello world&lt;/div&gt;">
+    <trix-editor input="my_input" autofocus placeholder="Say hello..."></trix-editor>`

src/test/test_helpers/fixtures/editor_with_image.js

@@ -1,5 +1,9 @@
+import * as config from "trix/config"
 import { TEST_IMAGE_URL } from "./test_image_url"
 
 export default () =>
-  `<trix-editor input="my_input" autofocus placeholder="Say hello..."></trix-editor>
-  <input id="my_input" type="hidden" value="ab&lt;img src=&quot;${TEST_IMAGE_URL}&quot; width=&quot;10&quot; height=&quot;10&quot;&gt;">`
+  config.editor.formAssociated ?
+    `<trix-editor autofocus placeholder="Say hello...">ab<img src="${TEST_IMAGE_URL}" width="10" height="10"></trix-editor>
+    ` :
+    `<trix-editor input="my_input" autofocus placeholder="Say hello..."></trix-editor>
+    <input id="my_input" type="hidden" value="ab&lt;img src=&quot;${TEST_IMAGE_URL}&quot; width=&quot;10&quot; height=&quot;10&quot;&gt;">`

src/test/test_helpers/fixtures/editor_with_toolbar_and_input.js

@@ -1,6 +1,14 @@
+import * as config from "trix/config"
+
 export default () =>
-  `<ul id="my_editor">
-    <li><trix-toolbar id="my_toolbar"></trix-toolbar></li>
-    <li><trix-editor toolbar="my_toolbar" input="my_input" autofocus placeholder="Say hello..."></trix-editor></li>
-    <li><input id="my_input" type="hidden" value="&lt;div&gt;Hello world&lt;/div&gt;"></li>
-  </ul>`
+  config.editor.formAssociated ?
+    `<ul id="my_editor">
+      <li><trix-toolbar id="my_toolbar"></trix-toolbar></li>
+      <li><trix-editor toolbar="my_toolbar" autofocus placeholder="Say hello..."><div>Hello world</div></trix-editor></li>
+    </ul>
+    ` :
+    `<ul id="my_editor">
+      <li><trix-toolbar id="my_toolbar"></trix-toolbar></li>
+      <li><trix-editor toolbar="my_toolbar" input="my_input" autofocus placeholder="Say hello..."></trix-editor></li>
+      <li><input id="my_input" type="hidden" value="&lt;div&gt;Hello world&lt;/div&gt;"></li>
+    </ul>`

src/test/test_helpers/fixtures/editors_with_forms.js

@@ -1,11 +1,21 @@
+import * as config from "trix/config"
+
 export default () =>
-  `<form id="ancestor-form">
-    <trix-editor id="editor-with-ancestor-form"></trix-editor>
-  </form>
+  config.editor.formAssociated ?
+    `<form id="ancestor-form">
+      <trix-editor id="editor-with-ancestor-form"></trix-editor>
+    </form>
+    <form id="input-form"></form>
+    <trix-editor id="editor-with-input-form" form="input-form"></trix-editor>
+    <trix-editor id="editor-with-no-form"></trix-editor>
+    ` :
+    `<form id="ancestor-form">
+      <trix-editor id="editor-with-ancestor-form"></trix-editor>
+    </form>
 
-  <form id="input-form">
-    <input type="hidden" id="hidden-input">
-  </form>
-  <trix-editor id="editor-with-input-form" input="hidden-input"></trix-editor>
+    <form id="input-form">
+      <input type="hidden" id="hidden-input">
+    </form>
+    <trix-editor id="editor-with-input-form" input="hidden-input"></trix-editor>
 
-  <trix-editor id="editor-with-no-form"></trix-editor>`
+    <trix-editor id="editor-with-no-form"></trix-editor>`

src/test/test_helpers/fixtures/form_associated.js

@@ -0,0 +1,4 @@
+document.head.insertAdjacentHTML(
+  "beforeend",
+  `<meta name="trix-editor-formAssociated" content="true">
+`)

src/test/test_helpers/test_helpers.js

@@ -56,6 +56,10 @@ export const testIf = function (condition, ...args) {
   }
 }
 
+export const testUnless = function(condition, ...args) {
+  testIf(!condition, ...args)
+}
+
 export const { skip, test } = QUnit
 
 const waitForTrixInit = async () => {

src/trix/config/editor.js

@@ -0,0 +1,5 @@
+const config = {
+  formAssociated: false
+}
+
+export default config

src/trix/config/index.js

@@ -2,6 +2,7 @@ export { default as attachments } from "./attachments"
 export { default as blockAttributes } from "./block_attributes"
 export { default as browser } from "./browser"
 export { default as css } from "./css"
+export { default as editor } from "./editor"
 export { default as fileSize } from "./file_size_formatting"
 export { default as input } from "./input"
 export { default as keyNames } from "./key_names"